New ways to leptogenesis with gauged B−L symmetry

We show that in supersymmetric models with gauged B−L symmetry, there is a new source for cosmological lepton asymmetry. The Higgs bosons responsible for B−L gauge symmetry breaking decay dominantly into right-handed sneutrinos N˜ and N˜∗ producing an asymmetry in N˜ over N˜∗. This can be fully converted into ordinary lepton asymmetry in the decays of N˜. In simple models with gauged B−L symmetry we show that resonant/soft leptogenesis is naturally realized. Supersymmetry guarantees quasi-degenerate scalar states, while soft breaking of SUSY provides the needed CP violation. Acceptable values of baryon asymmetry are obtained without causing serious problems with gravitino abundance.